Trewhella, The Final Chapter?

We have the following from our correspondent Down Under, Rob Isdale:

The World Wide Web has certainly lived up to its title.  One of the many visitors to Roy and Richard's Small Engine web site recently, was Dennis Trewhella, and it was a pleasant surprise for him to see and read the little article that I wrote about the Trewhella hot air engine that Olaf Berge has built from the drawings and information in the 1897 patent number 588,509.

Dennis lived in Victoria until his engineering occupation took him to England.  After reading about William Trewhella, his grandfather’s younger brother, he found a telephone number for me in Brisbane, and through a few phone calls and emails to me and to Olaf, we have been interested to learn some further information about William Trewhella, his brother and the engineering business.

Dennis is able to add some important facts about William Trewhella's hot-air engine activities, and we have asked him to set out some of the details here, as an addition to my article.  So, thank you Dennis, - it's over to you

Thank you Robert, it was indeed a pleasant surprise to read about Will Trewhella’s invention and Olaf Berge’s fine work in recreating it.  I should also thank Peter Saywell of ‘Trewhella Ltd’ UK for bringing the website to my attention.  

When I read your article I immediately contacted Nancy Burns whose father, the late George Trewhella, was MD of Trewhella Bros.  Nancy had fortuitously been sifting some of his papers.  She came up with some newspaper articles and personal reminiscences for us.

From the ‘Kyneton Guardian’ of 29 September 1964 (slightly edited for clarification):

“In 1888, two brothers William and Benjamin Trewhella started sawmilling, near the home farm at Blue Mount, south of Trentham in the Central Highlands of Victoria.

“William was an engineer who set his mind to improving methods in the mill - the original Trewhella jack being one of the first fruits of his efforts.  It proved a very useful implement for sawmillers, farmers and others, having heavy lifting to do.

The timber on the mill site was cut out by about 1893, when the brothers dissolved partnership.  William came to Trentham and built the ‘Sunnyside Foundry’ to carry on jack manufacture, while Benjamin continued as a sawmiller on various sites until 1903, when they joined in partnership again.  Benjamin took over a lot of the office work to give William more time for developing new ideas. [KG 29 Sep 1964] 

The engineering firm of ‘Trewhella Bros’ grew out of the renewed partnership, but it was apparently during the ten years 1893-1903 that Will Trewhella developed his hot air engine. George Trewhella wrote in 1969  "In the 1890's William did a lot of experimenting with hot air engines, and for a time drove his shop with the largest one he made."

So let’s hand over to an unknown reporter for the ‘Kyneton Guardian’ of Tuesday January 21st, 1896 under the headline:

Trewhella's Patent Hot Air Motor


"There was a large attendance, including a number of ladies, to witness the public trial of the above motor, which took place at Mr. W. Trewhella's Sunnyside Iron Works on Saturday afternoon.

"Great Interest was taken in the working of the motor, and the test was considered highly satisfactory.

The leading features of the invention are perfect safety, great saving in fuel, and entire saving of water.

The usual loss of time in getting up steam in other engines is also saved and it is estimated that all the fuel used during the trial, of some three or four hours, would not be sufficient to get up steam in an ordinary steam engine of the same power.

"The present motor has been tested up to six h.p., and the amount of fuel consumed is from 3 lb. to 4 lb. per hour.

"In larger motors, the amount of fuel required is expected to be less, and from the successful results of the present one, there does not appear to be any limit to the amount of power that may be obtained on the same principle.

"The power of the engine is obtained from the expansion of air by heat; the exact and detailed operation of the mechanism for effecting this purpose is not easily conveyed to the lay mind without the aid of diagrams, but the principle is simple in action and easily understood.

"In a vertical cylinder, open at the top and fitted with a closed furnace at the bottom, are two pistons; the upper or power piston being packed air tight and traversing about one-third of the upper end of the cylinder performs the functions of transmitting the power developed by the expansive forces of air through suitable mechanism to the crank shaft.

"The lower or displacer piston is simply a long, hollow vessel fitting the cylinder loosely, operated by means of a piston rod passing through the power piston and connected with the outer mechanism, and by its motion, draws in a charge of cool air under the power pistons at one portion of the revolution, and later passes the charge through pipes into the furnace.

There it becomes heated by the combustion of the fuel, and following well known laws of gases it expands, and in doing so, forces the piston out in the same manner as steam in an ordinary steam engine.

"After having done its work, the air is allowed to exhaust through a suitable valve and up the chimney.

"Fuel is fed into the furnace by means of a drum revolving air-tight into a semi-cylindrical piston and having a number of pockets in its circumference, each of which picks up a few coals from the hopper, and in revolving drops them in. a passage in the piston into the furnace.

"In order to start the engine, a fire is lit in the furnace and allowed to warm up a little, when the lighting door is closed, and a pull at the fly-wheel starts the engine, the whole operation taking but a few minutes.

"On larger engines, a reservoir of compressed air may be used for starting.

"Much time and experiment has been devoted to perfecting the details of the mechanism; also in controlling the heat, for the hot air, like fire, is a bad master which has exhausted the resources of many a scientist and engineer since the beginning of the century and a servant which will, undoubtedly, encroach very largely on the realm of steam before the century closes.

"Arrangements have been made to exhibit the motor at the exhibition at Ballarat, and it is to be sent there this week." [KG 21 Jan 1896]

Some seventy years later, on July 2 1966, the ‘Kyneton Guardian’ revisited the above story in an interview with George Trewhella a couple of years after his retirement and the sale of Trewhella Bros to interests outside the family.  Another anonymous reporter continues:

“Discussing this with Mr. George W. Trewhella, of Trentham, we learnt that the W. Trewhella mentioned, was his uncle.

“Mr. Trewhella also said that he remembers well the occasion and also that the engine was not marketed.

“At least four or five were manufactured, but kerosene oil engines quickly superseded the hot air ones.

“Mr. Trewhella said that the hot air engine, of that time, was a rather heavy and cumbersome thing, weighing anything from three to four tons for a six horsepower unit.

“Four or five of these were manufactured at Trentham, but his uncle had lost heavily on those manufactured as it had not proved to be a profitable undertaking.

“Yet he had had the satisfaction of putting Trentham on the map at that time, as his machines created a lot of public Interest.

“The oil engine was being developed at the same time and these could be constructed in a much smaller space and were much lighter.

“The boiler of the hot air and steam engines was the main stumbling block.

“Mr. Trewhella said that his uncle had designed his engine so that his fire was inside the cylinder.  This was done to overcome the heat loss which was a big factor against hot air engines. [KG 2 July 1966]

So there it is Robert, the rumour is true: there was a Trewhella hot air engine – several in fact.  Not, strictly speaking, products of ‘Trewhella Bros.’, but products of the genius of Will Trewhella at his Sunnyside Foundry: the foundry where Trewhella Bros., in the 20th century sense, came into being.

I guess the next question is ‘are there any bits of the original engines left?’.  I spoke to Maurice Scala, one of Will’s grandsons and the last member of the family to work at the foundry.  He was there until 1995.  Casting ceased very soon afterwards and the building is now used for other purposes, though two independent companies still produce ‘Trewhella’ jacks elsewhere: one in Ballarat and the other in Birmingham.

 Maurice reminded me that there had been two large auctions of equipment at Trentham and nothing now remains.   However, some years ago George Trewhella had commented that, in 1903, a disused air engine had been converted into a hydraulic pump and press for use in the foundry.  I can remember the press and its cylinders - perhaps the records of the auctioneers could reveal their destinations.

Will Trewhella took many photographs.  Perhaps the heat engine features in some of them.  I believe that some of his grandchildren were sorting out his papers and the negatives: perhaps more information will come to light.